Multiple wheel grinding machine



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MULTIPLE WHEEL GRINDING MACHINE Filed Dec. 1, 1951 ll Sheets-Sheet ll z 349 aw firz/erztor O/VA E. HILL EyMLAeJIaK fic'torney Patented Aug. 11, 1953 UNITED STATES PATENT OFFICE;

MULTIPLE WHEEL GRINDING MACHINE.

Oiva E; Hill; West Boylston, Massz, assignor to Norton Company, Worcester, Mass., 8.- corpo-- ration. of. Massachusetts Application December 1, 1951, Serial No. 269,372

17 Claims.

The invention relates to grinding machines, andmore particularly to a, cylindrical-type grinding-machine.

One object of the invention is to provide, a simpleand thoroughly practica1 machine for simultaneous-l'y grindin a plurality of spaced cylindrical portions on a workpiece. Another object'isto provide an automatically actuated truing mechanism for truinga grinding wheel after a predetermined number of workpieces have been round. Another object is to. provide a. truing apparatus with an automatically actuated indexing mechanism for indexing the diamond or truing tool after each truing operation. Another object is to provide a gauging mechanism automatically to' re-set the diamond or truing tool after each truingoperation and indexing thereof.

A furtherobject of the'invention is to provide a truing apparatus" havin a plurality of diamonds or truing tools. controlled; by a forming bar simultaneously to. true the peripheries of a plurality of spaced grinding wheels. Another object is to. provide an electricallycontrolled truing apparatus having" an; automatic cycle of operation which may be initiated manually or automatically after a predetermined number of workpieces have been ground. Another object of the invention is to provide a gauging mechanism automatically to re-set all of the diamonds or truing tools after an indexing mechanism thereof. Other objects will be in part obvious or in part pointed out hereinafter.

One embodiment of the invention has been illustrated in the drawings in which:

Fig. l is a front elevation of the improved grinding machine Fig. 2 is a right-hand end elevation of the machine;

Fig.3 is a plan view of the machine;

Fig. 4 is a hydraulic diagram of the actuating and control mechanisms of the machine;

Fig. 5 is an electrical wiring diagram of the electrical controls'of the machine;

Fig. 6 is a vertical sectional view, on an enlarged scale, through the wheel spindle showing Fig. 9 is; a fragmentary plan view, on an enlarged; scale', of the grindingwheel spindle reciprocating mechanism;

Fig; 10'is. a detail plan view, on an enlarged scale, of the forming bar;

Fig. 11 isa fragmentary horizontal sectional View, on: an; enlarged; scale, taken approximately on. the line H-l'l of Fig. 2, through a portion of themechanism formoving, the wheel guard to andfrom an operative position; 12 is a fragmentary vertical sectional view, on an enlarged scale, taken approximately on the line l2l2 of Fig. 3,.through aportion of the mechanism. for actuating the wheel guard;

Fig; 13 is a fragmentary rear elevation, on an enlarged scale, taken approximately on the line l3:|3 of Fig. 2; of the vertically movable truing tool gauge slide.

Fig. 14 is a fragmentary vertical sectional view, on. an enlarged scale, taken approximately on theiline. l.4"l4" of Fig. 3,, through the truing apparatus feedingmechanism;

Fig. 15 is a, fragmentary vertical sectional view on an enlarged scale, taken approximately on the line |5-|5' of Fig. 3, through the manually operable adjusting mechanism for the truing apparatus; crossv slide v Fig. 1'6"is a fragmentary vertical sectional view,

'on an enlargedscal'e, taken approximately on the lin |6|Bj ofv Fig. 7, through. the feed mechanism, comp sator;

Fig. 17' is an elevation, on. an enlarged scale, of'the compensator;

Fig. 18; is. a horizontal; sectional view, taken approximately on the line l8.l8 of Fig. 17, throughthecompensator;

Fig. 19. is a diagrammatic View of the hydraulic compensator motor;

units;

Fig. 21 is a p an w of thev truing tQol unit s h Wn; in Fig.v 20; with the top plate, br k away to more, clearly illustrated, construction;

22 is 1: !i n enlar cdscale, taken approximately on the line. zz. zz; of

Fig. 23; is a fragmentary secj',ior1a1. ie an enlar disc la. t lk r-r approximately on t line ZI3.Z.3.I' of: Fig- 2 sh wing; theindexing mechanism for; the.v truing: tool; Fig. 24 is a sectional view, on an enlar ed scale. taken. approx mately on. the; line 2.4-2.4; of

each other.

a Fig. 23, through the truing tool and the indexing mechanism therefor; and

Fig. 25 is a cross-sectional view, taken approximately on the line 25-25 of Fig. 24, through the ball clutch portion of the truing tool indexing mechanism.

An improved hydraulically operated electrically controlled grinding machine has been illustrated in the drawings comprising a base 38 which supports a longitudinally traversable work supporting table 3|. on a flatway 32 and a V-way 33 formed on the upper surface of the base 38. The table 3| serves as a support for a headstock 34 and a footstock 35 which are provided with work supporting centers 36 and 31 respectively for rotatably supporting a workpiece for a grinding operation.

The table 3| may be moved longitudinally relative to the base 38 by a suitable traversing mechanism such as for example a manually operable traversing mechanism comprising a hand traverse wheel 48 mounted on a rotatable shaft 4| (Fig. 1). The shaft 4| supports a gear 42 which meshes with a gear 43 mounted on a rotatable shaft 44. The shaft 44 is provided with a gear 45 which meshes with a rack bar 46 depending from the under side of the table 3|. It will be readily apparent from the foregoing disclosure that a rotary motion of the hand wheel 48 will be transmitted through the gear mechanism above described to impart a longitudinal movement to the table 3|. The direction of rotation of the hand wheel 48 serving to determine the direction of movement of the table 3|.

The headstock 34 is preferably driven by an electric motor 58 which is mounted on the upper surface thereof. The motor 58 is provided with an armature shaft carrying a stepped V- groove pulley 52. The pulley 52 is connected by a V-belt 53 with a stepped V-groove pulley 54 mounted on a rotatable shaft 49. The shaft 49 is provided with a pulley 55 which is connected by a V-belt 56 with a pulley 51 mounted on a rotatable shaft 58. The shaft 58 is provided with a sprocket 59. nected by a link chain 68 with asprocket 6| mounted on a headstock spindle 62. The driving mechanism above described is contained within a belt. guard 63 (Figs. 1, 2 and 3).

A wheel slide base 64 is fixedly mounted on the machine base 38 and serves as a support for a transversely movable wheel slide 85. The wheel slide base 64 is provided with a flatway 66 and a V-way 61 upon which the wheel slide 65 slides. The wheel slide 65 supports a rotatable grinding wheel spindle 68 in a pair of spaced bearings 69 and I8. The bearings 69 and 18 are in turn supported by a pair of sleeves 69a and 180. respectively. The outer surfaces of the sleeves 89a and 18a are cylindrical in shape and are supported by a semi-cylindrical surface II and I2 formed on the wheel slide 65. A pair of removably mounted bearing caps 13 and I4 surround the upper portion of the sleeves 69a and 18a respectively and are removably fastened to the wheel slide 65 to facilitate removal of the wheel spindle 68. The wheel spindle 68 is arranged to support a plurality of spaced grinding wheels I5, a, 15b and 150. Spacing collars "I8. 16a, and 16b are supported by the wheel spindle I58 and serve to position the grinding wheels in the desired spaced relationship with A pair of flanges I1 and 18 are fastened to the wheel spindle 68 by clamping The table 3| is supported The sprocket 59 is con- A bolts (not shown) to facilitate clamping the grinding wheels and sleeves to the spindle 68.

The grinding wheel assembly is partially surrounded by a wheel guard 84 (Fig. 7) the upper portion 85 of which is pivotally supported on a rock shaft 86 to facilitate movement of the portion 85 to an inoperative position during a. wheel changing operation.

A manually operable mechanism is provided for moving the hinged portion 85 of the wheel guard 84 to and from an inoperative position. This mechanism may comprise a hand wheel 81 mounted on a shaft 88 which is rotatably supported in anti-friction bearings 89 and 98. The bearings 89 and 98 are mounted within a housing 9| carried by the wheel slide 65. The shaft 88 (Fig. 11) is provided with a bevel gear 92 which meshes with a bevel gear 93 mounted on the end of a rotatable shaft 94 (Figs. 11 and 12). The shaft 94 is journalled in spaced antifriction bearings 95 and 96 which are supported within the housing 9 I. A worm 9I either formed integral with or fixedly mounted on the shaft 94 and meshes with a worm gear 98 (Fig. 12) which is keyed onto the end of the rock shaft 86. The hinged portion 85 of the wheel guard 84 is also keyed to the shaft 86 so that a rotary motion of the hand wheel 81 will be imparted through the mechanism just described to swing the hinged portion 85 to and from an operative position.

A suitable driving mechanism is provided for rotating the wheel spindle 68. The hinged portion 85 of the wheel guard 84 is provided with a. plane upper surface I88 which serves as a support for a motor slide base |8| which supports an electric motor I82. The motor I82 is provided with an armature shaft I83 (Figs. 1 and 2) having a multiple V-groove pulley I84 fixedly mounted thereon. The pulley I84 is connected by multiple V-belts I85 with a multiple V-groove pulley I86 whichv is keyed onto the right-hand end of the wheel spindle 68 (Fig. 6). The driving mechanism above described is enclosed within a belt guard I81 (Figs. 1, 2 and 3).

A suitable feeding mechanism is provided for causing a transverse movement of the wheel slide 65 which may comprise a rotatable feed screw I I8. A rotatable nut III surrounds and meshes with the feed screw II 8 and is rotatably supported within a housing 2 depending from the under side of the wheel slide 65 (Fig. 7). The righthand end of the feed screw H8 is supported in anti-friction bearings |I3 carried by a slidably mounted sleeve ||4 which is arranged to slide Within a cylindrical aperture I|5 formed in a housing I|6 formed integral with the wheel slide base 64. The left-hand end of the feed screwI I8 is provided with a cylindrical portion II! which is slidably keyed within a rotatable sleeve H8. The sleeve H8 is journalled in an anti-friction bearing II9 carried by the housing I I6 on the under side of the wheel slide base 64. A rotatable shaft I28 is slidably keyed within the left-hand end of the sleeve H8. The left-hand end of the shaft I28 is journalled in an anti-friction bearing I2| carried by the base 38. A gear I22 is mounted on the left-hand end of the shaft I28 and meshes with a gear I23 mounted on a rdtatable shaft 24. The shaft I24 carries a gear I25 which meshes with a gear I26 which is arranged to be rotated by a manually operable feed wheel I21. It will be readily apparent from the foregoing disclosure that a rotary motion of the hand wheel I21 will be imparted through the mechanism above describedv to impart a rotary motion to the feed. screw H and thereby impart a transverse feeding movement to the wheel slide 65: The direction of rotation. of the feed wheel I21 will determine the direction of movement of the wheel slide 65.

A hydraulically operated mechanism is provided for rapidly moving the wheel slide 651to andfrom an operative position. This mechanism may comprise a cylinder I30 containing a slidably mounted piston I3I. which is connected-to one. end, of apiston rod I32. The piston rod I32 and cylinder I30 are arranged in axial alignment with the feed screw H0. The left-hand end of the piston rod I32 (Fig. 7) is connected tothe slidably mounted sleeve I'M. A dashpot I33 is provided. to cushion the rearward movement of the piston I3I.

A hydraulic system isprovided comprisin a fluid pump I34 (Fig. 4) driven by an electric motor I35 (Fig. for supplying fluid under pressure. for operating the various parts of the machine. The pump I34 draws fluid through a pipe I361 from a reservoir I31 and forces fluid under pressure through a pipe I38. An adjustable relief valve I39 is connected. to the pipe line I38 to exhaust excess fluid under pressure directly to the reservoir I31 in order to maintain a substantially constant pressure within the pressure pipe i313. Fluid under pressurefrom the pipe I38 passes to a control valve I40. The valve I40 is a pistontype valve containing a slidably mounted valve member I4I having a plurality of valve chambers I42, I43 and I44 formed. in the periphery thereof. The slidably mounted valve member I4I is also provided with acentral. aperture to facilitate passage of fluid therethrough.

A pilot valve I46 is provided for controlling the endwise movement of the valve member I4I. A compression spring I41. serves normally to maintain the pilot valve in a right-hand end position (Fig. 4). A solenoid S1 is provided which when energized. serves to shift the pilot valve toward the left. The pilot valve I46 controls the passage of fluid under pressure through either a passage I49. or a passage I50 to a pair or end chambers I5I' and I52 respectively.

In the position of the valve I40 (Fig. 4) fluid from the pressure pipe. I38 enters the valve chamber I43 and passes through the pilot valve I46, through the passage I50 into theend chamber I52 to: move the slidably mounted valve member I4I to a left-hand end. position. In this position of the valve member I4.I fluid from the pressure pipe I38 entering the valve chamber I43 also passes through a pipe I53 to a control valve I54.

The control valve I54 is a piston-type valve containing a slidably mounted valve member I55 having a plurality of valve chambers I56, I51 and I58 formed in the periphery thereof. A pilot valve I59 is provided for controlling the shifting movement of the valve member I55. A compression spring I60 normally holds the pilot valve in a right-hand end position and a solenoid S9 is provided which when energized serves to shift the pilot valve into a left-hand end position. The pilot valve I59 controls the passage of fluid through either a passage I6I or a passage I62'into a pair of end chambers I63 and I64'respectively. The valve member I55 is provided with a central aperture to facilitate passage of fluid therethrough. In the position of the valves I54, and I59, fluid from the pressure pipe I 38 passes through a pipe I48, through the passage I62 into the end chamber I64 to move the valve member I55. toward theleft intoa left-hand endposition. Inthis position of the valve member I 55 fluid under pressure passing; through the pipe I53: enters the valve chamber I58, passes: through. the central passage I65, into the valve chamber I56 and then through a pipe I66 into a cylinder chamber I61 in the cylinder I30. to causethe piston. I3I: to move toward the right thereby causing a rearward movement of the wheel slide 65.. During movement of the piston I3I toward. the right, fluid within a cylinder chamber I68 may exhaust through a pipe I69 into the valve chamber I44 in the control valve I40, through the central passage I45, through the valve chamber I42, and through a pipe I10; a throttle valve ITI into a common exhaust pipe line I12 which returns fluid to the reservoir, I31. It will be readily apparent from the foregoing disclosure that the setting of the throttle valve I1I' will determine the rated exhaust of fluid from the cylinder chamber I68 and thereby control the rate of rearward movement of the wheel slide 65.

During the initial rapid approaching movement of the piston I3I and the wheel slide 65, fluid within the cylinder chamber I61 may exhaust through the pipe I 66 at a rate controlled by the throttle valve I1I After the piston I3I covers the end of the pipe I66, fluid may exhaust from the cylinder chamber I61 througha pipe I66'a and through a throttle valve I08 into the pipe I66. The throttle valve I08 serves to slow down the rapid approaching movement of the piston I 3| before it reaches the end of its stroke toward the left (Fig. 4). A ball check valve I09 serves to bypass fluid around the throttle valve I08 to facilitate a rapid rearward-movement of the piston I3I to an inoperative position.

The dashpot I33 serves to cushion the rearward movement of the piston I3I to slow down the rearward movement of the wheel slide 65. As the piston I3I approaches its rearmost position, a rearwardly extending projection of the piston rod I32 engages the piston of the dashpot I33 and forces fluid out through a pipe I13 and a throttle valve I14. By regulating the throttle valve I14 the extent of the cushioning action may be varied as desired. A ball check valve I15 is pro.- vided between the pipe I69 and the pipe I13to prevent fluid under pressure from passing through in a direction toward the left (Fig. 4).

A suitable mechanism is provided for imparting a rotary motion to the feed screw II oto pro.- duce the desired grinding. feed. of the grinding wheels 15. This. mechanism may comprise a feed cylinder I (Fig. 4) which contains a slidably mounted piston I 8I. The piston I8I is provided with a rack'bar I82 which meshes with a gear I83, The gear I83 meshesv with thegear I25 so that an endwise movement of the piston I 8|. will impart a rotary motion to the feed screw IIO. When fluid under pressure is passed through a pipe I84 into a cylinder chamber I85, the piston I8I will move toward the right to rotate the gear I83, the gear I25 tov impart a rotary motion to the feed screw II 0 so as to cause a forward feeding movement of the wheel slide '65. During this forward feeding movement, fluid within a cylinder chamber I86 exhausts through a pipe I81.

A control valve I88 is provided for controlling the exhaust of fluid from the feedcylinder I80. The valve I88 is a. piston type valve having a slidably mounted valve member I89 having a plurality of valve chambers I90, I9I and I92 formed in the periphery thereof. A pilot valve I 93.is provided for actuating the; valve. member I89. The pilot I93 is normally held in a righthand end position by a compression spring I94. A solenoid SIO is provided which when energized serves to shift the pilot valve into a left-hand end position. Fluid under pressure from the main pressure line I38 passes through a pipe I95 and is directed either through a passage I96 or a passage I91 by the pilot valve I 93. Fluid passing through either the passage I96 or the passage I91 enters an end chamber I98 or an end chamber I99 respectively to cause an endwise movement of the valve member I89.

When the machine is set in motion the solenoid SIO is normally energized so that the valve member I89 is in a right-hand end position so that fluid exhausting from the feed cylinder I80 through the pipe I81 enters the valve chamber I 9| and is blocked by a ball check valve 204 so that no fluid can exhaust from the feed cylinder chamber I86 while the solenoid SIO remains energized. When the solenoid SIO is deenergized the valve member I89 is moved to a left-hand end position as shown in Fig. 4 so that fluid exhausting through the pipe I81 from the feed cylinder chamber I86 may pass through the valve chamber I9I, through a throttle valve 206 into the pipe I53 and out through valve I40 when energized and through the exhaust pipe I12 into the reservoir I31. A ball check valve 281 is provided so that when fluid under pressure is passed through the pipe 205 from the control valve I40, it may by-pass the throttle valve 206.

A shuttle type backlash control valve 208 is provided for rapidly taking up the backlash in the gear train of the feed mechanism. The backlash valve 208 is a piston type valve having a valve chamber 209. As the valve chamber 289 moves either toward the right or toward the left, fluid exhausting through the pipe I81 from the feed cylinder chamber I86 may pass through the valve chamber 209 and through a pipe 2I0 into the main exhaust line I12. This additional exhaust of fluid from the feed cylinder chamber I86 facilitates an initial rapid motion of the piston I8I toward the right so as to take up the backlash in the gears and the feed screw as the grinding wheels move into grinding engagement with the workpiece being ground. The movement of the backlash valve 208 is controlled by the admission of fluid to either the end chamber 2 or the end chamber 2I2. A throttle valve 2I3 controls the speed of movement of the backlash valve 208 toward the right and a ball check valve 2 serves to allow fluid to by-pass the throttle valve 2 I3 when the fluid is moving in the reverse direction. A throttle valve 200 in the pipe I84 serves to regulate the admission of fluid under pressure to the feed cylinder chamber I85 and also to the back-lash valve chamber 2 I I.

It will be readily apparent from the foregoing disclosure that the control valve I40 serves to control the admission to and exhaust of fluid from the cylinder I30 to control the rapid approaching and receding movement of the wheel slide 65. The control valve I54 serves to control the exhaust of fluid from the cylinder I30 to produce a shoulder feed for grinding a shouldered surface adjacent a peripheral surface on the workpiece being ground. The control valve I88 serves to control the body or grinding feed of the wheel to produce a slow controlled infeed of the wheel slide 65 during the grinding of a cylindrical portion on the workpiece being ground.

When a combined shoulder and body feed is desired, a switch 2I4 (Fig. is closed thereby rendering a circuit operative so that when the wheel slide 65 moves forward, a normally open limit switch LS9 will be closed to energize the solenoid S9 thereby slowing down the rapid approaching movement of the wheel slide 65 to a shoulder feed. The shoulder feed continues until the grinding wheel is about to move into engagement with a peripheral portion on the work at which point the forward movement of the wheel slide serves to open a normally closed limit switch LSIO so as to deenergize the solenoid SIO thereby positioning the valve I88 as shown in Fig. 4 to control the grinding feed on a body portion of the workpiece being ground.

A multiple wheel truing apparatus is provided whereby all of the grinding wheels may be simultaneously trued either by means of a manually initiated cycle or by an automatic cycle which is set in motion after a predetermined number of workpieces have been ground. This mechanism may comprise a truing apparatus cross-slide 220 (Fig. 8) which is supported by a dovetailed slide way member 22I which is fixedly mounted on the upper surface of the wheel slide 65. A suitable positioning and feeding mechanism is provided for the cross-slide 220 comprising a cross feed screw 222 (Figs. 4 and 14) which meshes with a rotatably mounted nut 223. The nut 223 is rotatably supported by antifriction bearings 224 and 225 carried by a depending housing 2I9 on the under side of the cross-slide 220. A shaft 226 is slidably keyed within a central aperture formed in the feed screw 222. The left-hand end of the shaft 225 is supported in an anti-friction bearing 221 which is carried by the dovetailed slideway member 22 I. A worm gear 228 is keyed onto the shaft 226 and serves in a manner to be hereinafter described to impart a compensating adjustment to the feed screw 222. A shaft 229 is fixedly mounted in the central aperture on the right-hand end of the feed screw 222. The shaft 229 is supported by an anti-friction bearing 230 supported within a piston 23I. The piston 23I is in turn slidably mounted within a cylinder 232. When fluid under pressure is passed through a pipe 233 into a cylinder chamber 234 at the righthand end of the cylinder 232, the piston 23I will be moved toward the left (Fig. 14) to cause a forward positioning movement of the cross-slide 220. The forward movement of the slide 220 will continue until a stop surface 235 on the left-hand end of the feed screw 222 (Fig. 14) engages a shoulder 236 formed on the hub of the worm gear 228. This movement of the cross-slide 220 serves to position the slide in an operative position for a truing operation.

A hydraulically operated mechanism is provided for withdrawing the cross-slide to a rearward or inoperative position comprising a cylinder 238 (Figs. 4 and 14) which is fixedly mounted on the cross-slide 220. The cylinder 238 contains a slidably mounted piston 239 which is connected to one end of a piston rod 240-. The other end of the piston rod 240 is fastened to an upwardly extending lug on the dovetailed slideway member 22I. It will be readily apparent from the foregoing disclosure that when fluid under pressure is passed through a pipe 265 into a cylinder chamber 243, the cross-slide 220 together with the cylinder 238 will be moved toward the right (Figs. 4 and 14) to Withdraw the truing apparatus to a rearward or inoperative position. During the rearward movement of the cylinder 238 fluid within a cylinder chamber 244 may exhaust through a pipe 245 into the main exhaust pipe I12 and also through a throttle valve 246 into the exhaust pipe I12. During the initial movement of the cylinder 238 toward the right, fluid may exhaust substantially unrestricted through the pipe 245 until the piston 239 covers the port at the end of the pipe 245 after which fluid must exhaust throu h the throttle valve 246. It will be readily apparent from the foregoing disclosure that by manipulation of the throttle valve 246, the final movement of the cross-slide 229 and the cylinder 238 toward the right (Figs. and 14) may be readily controlled.

In order to slow down the forward movement of the cross-slide 229 when moved toward the left (Figs. 4 and 14) into an operative position, a pipe 241 is provided which is normally inoperative. The pipe 241 connects with a ball check valve 248 and a throttle valve 249. As the piston 23I is moved toward the left by means of fluid under pressure within the cylinder chamber .234, no fluid can enter the pipe 241. After the piston 23! uncovers the port at the end of the end of the pipe 241, as the piston moves toward the left (Fig. 4), fluid under pressure within the chamber 234 may then be forced out through the pipe 241, the ball check valve 248 and the throttle valve 249 thereby to slow downthe forward approaching movement of the cross-slide 229.

A suitable control valve 259 is provided for controlling the admission to and exhaust a fluid from the cylinders 232 and 238. The valve 259 is a piston type valve comprising a slidably mounted valve member 25| having a plurality of valve chambers 252, 253 and 254 formed in the periphery thereof. The slidably mounted valve member 25l also containsa central passage 255. A pilot Valve 256 is provided for controlling the movement of the slidably mounted valve member 25l. The pilot valve 256 is normally held in a right-hand end position by a compression spring 251. A solenoid S6 is provided which'when energized serves to shift the pilot valve toa'left-hand end position.

Fluid under pressure from the pressure :pipe I-SB passes through a pipe 258, into the valve chamber 253 and through a passage 259 into the pilot valve 256. Fluid under pressure is directed by the pilot valve either through a passage 269 or a passage .26! into a pair of end chambers .262 and 2.63 respectively. The valve 259 is connected by a pipe .264 with the right-hand end of the cylinder 232 and by a pipe 265 with the right-hand end of the cylinder 238. posed in a pipe 291 which connects the control valve 259 with theexhaust pipe -I 12. ;By manipu lation of the throttle valve 256, the rate of the forward or-rearward movement-of the cross-slide 229 may be readily varied.

A manually operable mechanism is provided for actuating the feed screw 2 2 2 comprising-a manually operable hand wheel 219. The hand wheel 219 (Fig. 15) is mounted on the hight-handend of a rotatable shaft 21!. The shaft 2' is connected by a coupling 212 with a shaft 213 which is journaled in anti-friction bearings .214 and.21.5 respectively. A spiral gear 2.1.6 iskeyedonto the Athrot-tle valve 266 is interl journalled in an anti-friction bearing 285. A power operated mechanism is provided for imparting a rotary motion to the screw 283 to traverse the slide 289 longitudinally relative to the slide 229 in a direction parallel to the axis of the grinding wheel spindle 68. A V-groove pulley 266 is mounted on the left-hand end of the screw 283 (Fig. 8). The pulley 296 is connected by a V-belt 281 with a V-groove pulley 298 mounted on the rotary shaft of a rotary-type fluid motor 289. When fluid under pressure is passed through either the pipe 299 or the pipe 291, a rotary motion will be imparted to the motor 299 to rotate the traverse screw 283 and thereby imparta longitudinal traversing movement to the slide 289. A pair of throttle valves 292 and 293 are provided on opposite sides of the fluid motor 289 (Fig. 4) to facilitate controlling the speed of the motor in either direction. A ball check valve 294 is arranged in the pipe 29! to facilitate by-passing fluid around the throttle valve 293 so that the speed of movement of the slide 289 in either direction may be independently varied.

A control valve 295 is provided for controlling the admission to and exhaust of fluid from the fluid motor 289. This valve is a piston type valve having a slidably mounted valve member 296 which is provided with a plurality of valve chambers 291, 298, 299 and'399 formed in the periphery thereof. The slidably mounted valve member 296 is also provided with a central passage 39l. A pilot valve 302 is provided for controlling the passage of fluid through either a passage 393 or a passage 394 into end chambers 395, or 396 respectively to shift the slidably mounted valve member 296. The slidably mounted valve member 296 is normally held in a central position by balanced springs within the end chambers 395 and 396. The pilot valve 392 is similarly held in a central position by balanced springs. A pair of solenoids 88a and 881) are provided to shift the pilot valve 392 in either direction so, as to pass fluid under pressure from the pressure line I38 through a pipe 391 to produce a shifting movement of the slidably mounted valve member 296.

In order to facilitate truing the grinding wheels a predetermined amount at each pass of the longitudinal slide 289, it is desirable to provide an automatic compensator 3I2 automatically to rotate the feed screw 222 by a predetermined increment to reposition the truing tool slide 229 and at the same time to rotate the feed nut II I relative to the feed screw H9 to compensate for the reduction in size of the grinding wheels caused by the 'truing operation so that grinding may be resumed without the necessity of resetting the wheel feeding mechanism.

The compensator 3l2 (Figs. 16, 17, 18 and'19=) may comprise a fluid motor comprising a cylinshaft 213 and meshes with a spiral gear 21.1 which It will be der 3I3 containing a slidablyvmounted piston3 M which is fixedly mounted on one end of a piston rod 3|5. A piston type control valve 316 is provided for controlling the reciprocatory movement of the piston 3I4. This motor is identical with that disclosed in the U. .5. Patent No. 2,522,481 to D. W. Martin dated September 12, 1950 and the compensator as a unit is substantially the same as that shown in the prior U. S. Patent No. 2,522,485 to H. A. Silven and C. G. Flygaredated September 12, 1950, to which reference may be had for details of disclosure not contained herein. A pipe 319 connects the pipe .291 with the compensator -3 l2 and a pipe 3H connects the pipe 299 with the compensator 312 so that whenever fluid under pressure is passed through either the pipe 290 or the pipe 291 to cause a longitudinal traversing movement of the truing tool slide 280, fluid is also passed to the compensator 312 to advance the truing tool cross-slide 220 at the start of each longitudinal movement of the slide 280. The control valve 316 is shifted by the admission of fluid to either the end chamber 3!! or the end chamber 318. The rate of movement of the valve 3I6 is controlled by throttle valves 311a and 3l8a. Ball check valves 3l1b and 3l8b allow fluid to by-pass the throttle valves 3 Ha and 3 I 8a on the pressure side of the system. This motor being identical with the disclosure in the prior patent above referred to, reference may be had thereto for disclosure not contained herein. During each longitudinal shifting movement of the control valve 3I6, the piston 314 makes one complete reciprocation.

The piston rod 315 is provided with an arm 319 (Fig. 1'1) the upper end of which is provided with a yoke 320 which slides within opposed grooves 32| and 322 formed in a collar 323 fastened to a slide rod 325. The slide rod 325 is provided with a rack bar 326 which meshes with a gear segment 321. The gear segment 321 is rotatably supported on a shaft 328. The gear segment 321 is provided with a lug 329 having a stud 330 which supports a pivotally mounted spring pressed pawl 33I which engages a ratchet wheel 332 keyed on the end of the shaft 328. A spring pressed holding pawl 333 is mounted on a fixed stud 335 to prevent clockwise movement of the ratchet wheel 332. It will be readily apparent from the foregoing disclosure that during each reciprocation of the piston 314, the slide U rod 325 will be reciprocated through a similar stroke to oscillate the gear segment 321. During the clockwise movement of the gear segment 321, the feed pawl 33| rides idly over the teeth of the ratchet wheel 332 during the return counterclockwise motion Of the gear segment 321, the feed pawl 33! imparts a rotary motion to the ratchet wheel 332.

The shaft 328 is connected by a coupling 336 with a shaft 331 journalled in a bearing 338 carried by a housing 339. A bevel gear 340 is mounted on the left-hand end of the shaft 331 (Fig. 16). The bevel gear 340 meshes with a bevel gear 341 which is keyed on a rotatable shaft 342. The shaft 342 is provided with a worm 343 which meshes with a worm gear 228 (Figs. 14 and 16). The shaft 342 is also provided with a worm 344 which meshes with a worm gear 345 formed on the periphery of the feed nut Ill. It will be readily apparent that each time the compensator actuates to impart a rotary motion to the shaft 328, a feeding movement will be imparted to the feed screw 222 to advance the truing apparatus cross-slide 220 and at the same time a compensating adjustment will be made of the wheel feed nut HI to advance the grinding wheel slide 65 by an amount trued off the grinding wheel so that a grinding operation may be resumed without the necessity of resetting the feed mechanism.

A plurality of truing tool units 350, 350a, 350D and 3500 are each formed with dovetailed slide surfaces 35! to mate with a longitudinally extending dovetailed slideway formed on the upper surface of the longitudinally movable truing tool slide 280. Each of the truing tool units is provided with a clamping screw 352 to facilitate clamping the unit in the desired position on the slide 280. Each of the truing tool units 356 is provided with a diamond or truing tool 353 which 15 mounted in a manner to be hereinafter described.

The truing tool units are arranged on the slide 286 so that the diamonds 353 may be traversed or reciprocated longitudinally simultaneously to true the peripheries of the grinding wheels 15, 15a, 15b and 15c. Each of the truing tool units 350 is provided with a frame 348 having a longitudinally movable slide member 349. The slide member 349 is preferably supported by antifriction rollers so as to allow free and easy movement of the slide member 349 relative to the frame 348. Two sets of four rollers each are mounted in spaced relation to each other to support and guide the slide member 349. As illustrated in Figs. 20, 21 and 22 one set of rollers 355, 355a, 3551) and 3550 are respectively arranged to rotate about vertical axes. The rollers 355 and 355a are arranged to engage vertical guide faces 356 and 351 respectively formed on opposite sides of a guide rib 358 which projects upwardly from the slide member 349. Similarly the rollers 355D and 3550 are arranged to rotate about vertical axes and to engage guide faces 359 and 369 formed on opposite sides of a guide rib 36| which depends from the under side of the slide 349. The rollers just described serve to guide the rear end of the slide 349 and to hold the slide against lateral movement.

A smiliar set of rollers 365, 365a, 365D and a fourth roller (not shown) serve to guide the forward end of the slide 349 and to hold it against lateral movement. The rollers 365 and 365a are arranged to engage guide faces 366 and 361 formed on opposite sides of a guiding rib 368 which projects upwardly from the slide 349. Similarly roller 3651) and the fourth roller (not shown) engage opposite guide faces on a guide rib 369 which depends from the under side of the forward end of the slide 349. At least one of each pair of rollers is mounted with an eccentric adjustment to facilitate taking up any lost motion between the slide and the anti-friction rollers.

Two sets of spaced rollers 312 and 313 are arranged to engage guide faces 316 and 311 respectively formed on the upper and lower surfaces of the guide ribs 355 and 36l respectively. Similarly a pair of rollers 310 and 31! mounted adjacent to the forward end of the slide 349 are arranged to engage slide surfaces 314 and 315 formed on the upper and lower surfaces respectively of the guide ribs 368 and 369. At least one of each pair of rollers 312-313 and 310-311 are mounted with an eccentric adjustment to facilitate taking up backlash between the sliding parts. The rollers 310, 311, 312 and 313 are all mounted to rotate about horizontal axes and are arranged to maintain the slide 349 against vertical motion and to guide the slide toward and from the periphery of the grinding wheels during a truing operation. I

It is desirable to provide a suitable forming arrangement for controlling the movement of the truing tools as they are traversed across the peripheries of the grinding wheels. Each of the truing tool unit slides 349 are provided with a follower 380 (Fig. 21) which is arranged to engage the operative face of a forming bar 38I. The forming bar 38! is anchored by clamping screws 382 and 383 to the cross slide 220. A compression spring 384 is provided on each of the truing tool units to facilitate maintaining the followers 386 in operative engagement with the forming bar 381. The forming bar 38| is provided with a plurality of spaced operative faces 385, 385a, 3851) and 3850 which are arranged respectively tocontrol the path of. movement. of the diamonds or: truingtools 3.53. for simultanee ouslytruingthe faces of the grinding wheels 15. 15a, 15b and 1 5.0. The forming bar 38Lv is slotted and. a plurality of adjusting screws 309-381, 386a381a, 386b -381b and 386c38lc are provided to facilitate independent flexing of the faces 385,. 385a, 385b and 3050 relative. to the bar 38lso as to vary the path of travel. of. the respective diamonds 353 during a truingopera-- tion.

An indexing mechanism is. provided rotatably to index. the diamond or truing tool 353- aftereachtruing operation in order to present asharp cut-- ting edge on. the diamond for eachtruing opera.- tion. The indexing of the" diamond not onlyserves at all times-to provide a sharp cuttingedge for thetruing operation but also serves to minimize the wear upon the diamond; A gaugedeviceis provided cooperating with theztruing apparatus autormatically to reset the diamonds. in a precise location before each; truing operation. As illustrated in Figs. 23 and 24 the diamond. 35.3 is mounted in a nib 390 which: is supported. in. a sleeve 39! which is screw threaded ontothe-lefthand end of a rotatable shaft 392. The shaft 392 isrotatabl supportedwithin a central bore in a sleeve 393-. The sleeve 393. supporting the diamond indexing mechanism issupportedwithin a cylindrical bore 394. formed within an. enlarged head portion 395- formed integral with the truing toolslide 349-. The sleeve 393 is arranged to be clamped within the housing 395 by means of a. set screw 396.

A hydraulically operated mechanism is provided for clamping the diamond 353 and. shaft 392. in anindexed position. during a truing operation. This. mechanism may comprise a clamping plug. 39.! which. is slidably mounted within a transverse. aperture. within. the sleeve 393.. Theend of the. plug 391. engaging the shaft 392 may be either V-shapedor maybe formed. as a partial cylindrical surface. A slidably mounted cam 398 formed. onthe end. of. a piston. rod 399 engages the. clamping plug 391. The piston rod 399 is fixedly mounted to -a piston 40.0 which isslidably mounted within a. cylinder 40!. It will be readily apparent from the foregoing, disclosure that when fluid under pressure is passed through apipe 402. into a cylinder. chamber 403, the piston 400wi1l be moved. toward the left. (Fig. 23) causing. the. piston. rod. 399. and thecam 398.to also movetoward theleft toforce. the clamping plug. 391 into frictional clamping. engagement. with. the. periphery of the shaft 392 so as to clamp the diamond. 353' in an indexed. position for a. truing operation- Apiston404 is fastened to. the right-hand. end. of the shaft 392. The piston 404' slides within a cylinder 405. A sleeve 400 is rotatably supported on a reduced end portion 401 of the shaft 392. The periphery of the sleeve 406 is: provided with a pair of diametrically opposed. cam grooves'408" and; 409... The cam grooves 408" and 409 are engaged by follower studs 4"li0 and 411 which are fixedly mounted relative to the sleeve 393. A ball clutch. 412' is either formed integral with or fixedly mounted on the shaft 392'. The ball clutch 412 is'arranged sothat'when fluid under pressure is passed through a pipe" 413 into a cylinder chamber M4, the piston 404- will be moved downwardly without imparting a rotary motion to-the shaft 392-. When fluid un d'er pressure is passed through a pipe 415 into a cylinder chamber 416 to cause a movement of the sleeve 406" and the piston 404 toward the right,

the. ballclutch 4l2" locks the; shaft. 392-. tothe: sleeve. 406, so that the cam grooves 408;. and 410.9.

sliding on the fixed follower studs. Hi0 and; 41 I.

will impart a rotary indexing movement to. the shaft 392 andalso to. the. diamond ortruing. tool 353. A compression spring 4H is provided within acylinder chamber 414 normally to exert a pressure toward the left on the piston 404. so;

as. tomove the diamond 353; into engagement with a'gauge. plug 418.- after an: indexing mechanism. to rex-set the diamond for the next truing operation. The mechanism above described is thesame asthat provided. for each of the truing: tool:

units 350, 35011, 35.0band 3500. Only one unit has been illustrated in detail in Figs. 23 and. 24. and in the diagram (Fig. 4). Pipes 402-, 41.3 and 41.5 are-connected to each. of the truing tool units 350, 350a, 3501) and 35,00 for actuating the rotaryindexing mechanisms for the diamonds 353.

A gauging mechanismis provided for re-setting all of the diamonds: after each indexing mechanism. This mechanism may comprise a; vertically movable slide 420 which is arranged. to' slide in-a vertical direction ona dovetailed slideway 421' which is fixedly mounted on or formed integral. with the truing apparatus cross-slide- 22.0. (Figs. 3 and l3-)-. arranged to be moved vertically to and from an operative position by means of a cylinder 422 which is fixedly mounted relative to the truing tool cross-slide 220. The cylinder" 422- containsa slidably: mounted piston 423 which is connected by a piston rod- 424' with. a projection 42-5 of the gauge slide 420. The gauge slide 420 is normally maintained in a downward or operative position. When it is desired to move the-gauge slide to an inoperative position fluid under pressureis passed through: a pipe 426 into a cylinder chamber 421 to cause an upward movement of the: piston 423.. During this'movement. fluid with.- in a cylinder chamber 420- is. exhausted througha pipe 429.

The gauge slide 420" is provided with a plurality of adjustably mounted gauge plugs 418, 44011; 41 8b and- 41:80 eachof which is carried by an adjustably mounted supporting plate 430,.

off the; same diameter. The gauge plugs 41:8; are. adjustably mounted on: the gauge slide 420; and.

may be adjusted'relative thereto in case grinding wheels of different diameters are used on the If desirable longer gaugegrinding machine; plugs; 41:8; may be? utilized, the lengths; depending upon the diameters of the grinding wheels used.

The; gauge slide 420 isprovided with a pair of adjustable: mounted: screws 432- and 433. which are-arrangedto actuate a pair oflimit switches.

. is provided for clamping the bracket 460 inad.

The gauge slide 420 is 15 justed position on the slide 280. The stop bracket 466 is arranged to engage an adjustable stop plug 468 carried by the gauge slide 420. The stop mechanism above described serves to position the cross-slide 220 so that all of the diamonds 353 after an indexing movement thereof are maintained in engagement with the gauge plugs 4 8 by the compression springs 4 I 1.

A control valve 435 is provided for controlling the admission to and exhaust of fluid from the gauge slide cylinder 422. The valve 435 comprises a slideably mounted valve member 436 having a plurality of valve chambers 431, 438 and 439 formed in the periphery thereof. The valve member 436 is also provided with a central fluid passage 440. A pilot valve 44! (Fig. 4) is provided for controlling the shifting movement of the valve member 436. A compression spring 442 normally holds the pilot valve 44! in a righthand end position so that fluid under pressure from the main pressure pipe I38 passes through a pipe 443 into the valve chamber 438 and through a passage 444 into the pilot valve 44! and then through a passage 445 into an end chamber 446 to move the valve member 436 into a left-hand end position. During this movement of the valve member 436, fluid within an end chamber 446 may exhaust through a passage 441, through the pilot valve 44! and out through a pipe 449 which connects with the main exhaust pipe I12. A throttle valve 434 located between the control valve 435 and the exhaust pipe !12 serves to control the rate of fluid exhausting from the cylinder 422 and also the rate of movement of the gauge slide 420 to and from an inoperative position. The pilot valve 44! is provided with a solenoid S which when energized serves to shift the pilot valve into a left-hand end position thereby admitting fluid through the passage 441 into the end chamber 448 to shift the valve member 436 into a right-hand end position. In this position of the valve member 436 fluid under pressure passes through the pipe 426 into the cylinder chamber 421 to raise the piston 423 together with the gauge slide 420 upwardly into an inoperative position.

For a plunge cut grinding operation, it is desirable to provide a reciprocating mechanism for the wheel spindle 68. This mechanism may comprise a worm 410 mounted on the wheel spindle 68, The worm 410 meshes with a worm is formed as a yoked member surrounding a sleeve formed integral with the worm 410. The yoked portion of the arm 411 is provided with a pair of diametrically arranged rollers 419 and 480 which ride in a groove 48! formed in a sleeve which is an integral part with the worm 410. A compression spring 482 serves normally to maintain the stud 416 in the bottom of the yoke 415. It will be readily apparent from the foregoing disclosure that rotation of the spindle 68 will be imparted through the worm 410 and worm 41! to oscillate the connecting rod 414 which in turn imparts an oscillating motion to the arm 411 so as to impart an axial reciprocatory movement to the wheel spindle 68.

During a truing operation, it is desirable to stop the wheel spindle reciprocation in order to facilitate a precise truing of the grinding wheels. This is preferably accomplished by means of a hydraulically operated mechanism comprising a cylinder 483 which contains a slidably mounted piston 484. The piston 484 is connected to a piston rod 485. A compression spring 486 normally holds the piston 404 in a right-hand or inoperative position (Fig. 4). When it is desired to stop spindle reciprocation fluid under pressure is passed through the pipe 402 into a cylinder chamber 481 to move the piston 484 toward the right thereby causing the piston rod 485 to engage a screw 488 carried by the rock arm 411 and to rock the rock arm 411 in a counter-clockwise direction against the compression of the spring 482. This movement of the rock arm 411 shifts the stud 416 away from the bottom of the yoke 415 so that even though the connecting rod 414 is oscillated, no reciprocatory motion will be imparted to the wheel spindle 68.

A solenoid valve 450 is provided for controlling the admission of fluid to the pipe 402 so as to simultaneously admit fluid to the diamond clamp cylinder and to the spindle reciprocation stop cylinder 463. This valve comprises a slidably mounted valve member 45! having a valve chamber 452 formed in the periphery thereof. A compression spring 453 normally maintains the valve member 45! in a right-hand end position and a solenoid S! is provided which when energized serves to shift the valve member 45! into a left-hand end position. The valve member 45! is also provided with a central fluid passage 454. In the position of the valve 450 (Fig. 4) fluid under pressure from the main pressure pipe !38 passes through the valve chamber 452 and through a pipe 455 into an end chamber 456 of a valve 451. The valve 451 is normally held in a left-hand end position by means of a compression spring 456. The valve 451 is provided with a valve chamber 459 which is arranged so that when fluid is admitted to the end chamber 456, the valve chamber 459 connects a pipe 460 with the pipe M3 to cause a movement of the piston 404 toward the left (Fig. 23).

The passage of fluid through the pipe 460 is controlled by a solenoid valve 46! having a slidably mounted valve member 462. The valve member 462 is provided with a valve chamber 463 and a central passage 464. The valve member 462 is normally held in a central position by a pair of opposed compression springs. A pair of solenoids S20, and 62b are provided which when energized serve to shift the valve member 462 in either direction. When the solenoid 32a is energized, the valve member 462 shifts toward the right so that fluid from the pressure pipe I38 may pass through the pipe 460, through the valve chamber 459 and through the pipe 4!3 into the cylinder chamber 401 to cause a movement of the diamond 353 toward the left. This movement is obtained during the rearward movement of the truing tool crossslide 220 and is an idle stroke to condition the parts for an indexing movement of the diamond 353. When the solenoid 82b is energized, the valve member 462 shifts toward the left so that fluid under pressure from which the main pressure pipe I33 passes through the valve chamber 463 and through the pipe 4!5 through the cylinder chamber 4! 6 to cause the cam sleeve 406 and the piston 404 to move toward the right 17 (Figs. 4 and 23) to index the diamond353 for the next grinding operation.

A pair of work steady rests 490 and 491 may be provided on the work table 3| to facilitate steadying and supporting the workpiece against the thrusts of the grinding wheel. These steady rests may be of a type such as that shown in the prior U. S. Patent No. 2,567,620 to H. A. Silven dated September 11, 1951 in which a pair of work steadying shoes 492 and 493 are provided on each of the steady rests. These steady rest shoes as shown in the prior patent may be spring actuated to maintain the shoes in operative engagement with the workpiece during a grinding operation and a manual adjustment may be provided similar to that shown in the above mentioned prior patent. These steady rests have been illustrated diagrammatically in Fig. 4 in which a pair of compression springs 494 and 495 are provided normally to maintain the work shoes 492 and 493 respectively in operative engagement with the work during a grinding operation.

In order to provide an automatic withdrawal of the steady rest shoes after a grinding operation has been completed, a fluid cylinder 496 is providedcontaining a piston 491 which is operatively connected to the shoe 492. When fluid under pressure is passed through a pipe 498 into a cylinder chamber 499, the steady rest shoe 492 is moved toward the left into an inoperative position out of engagement with the workpiece being ground. Similarly a cylinder 500 is provided containing a slidably mounted piston 501 which is operatively connected to the shoe 493. When fluid under pressure is passed through the pipe 498 into a cylinder chamber 502, the work steadying shoe 493 will be moved to an inoperative position out of operative engagement with the work.

A solenoid valve 505 is provided for controlling the admission to and exhaust of fluid from the pipe 498. This valve comprises a slidably mounted valve member 506 having a valve chamber 501 formed in the periphery thereof. A compression spring 508 normally holds the valve member 506 in a right-hand end position and a solenoid S3 when energized is provided or shifting the valve member 506 toward the right. In the position of the valve member 506 (Fig. 4) when fluid under pressure is forced through the main pressure pipe 138, it passes into the valve chamber 531 and through a pipe 509 and a ball check valve 510 into the pipe 498. Fluid under pressure in the pipe 498 as previously described enters the cylinder chambers 499 and 502 to withdraw the work steadying shoes 492 and 493 respectivelyto inoperative positions. When the solenoid S3 is energized, fluid within the cylinder chambers 499 and 502 may exhaust through the pipe 498, through a throttle valve 511 and into the main exhaust line I12. By adjusting the throttle valve 511, the rate of movement of the shoes 492 and 493 under the released compression of the springs 494 and 495 respectively may be readily controlled.

A coolant supply system including a coolant fluid pump (not shown) which is driven by an electric motor 514 (Fig. is provided for supplying coolant either to all of the grinding wheelsor to all of the diamonds 353 during a truing Operation. A coolant supply pipe 515 is provided (Fig. 4) to pass coolant fluid to a control valve 5l6. The control valve 5|6is provided with a slidably mounted valve member 511 having a valve chamber 518 formed in the periphery thereof. When fluid under pressure is passed through the pipe 519, the valve member 5l1 is moved toward the right so that coolant fluid from the pipe 5| 5 may pass through the valve chamber 5l8 and through a pipe 520 to convey coolant fluid to all of the grinding wheels 15, 15a, 15b and 150. Similarly when fluid under pressure is passed through a pipe 521, the valve member 511 is moved toward the left thus cuttingofi fluid from the grinding wheels and passing coolant fluid from the pipe 515 through the valve chamber 5|8 and through a pipe 522 toa nozzle 523 on each of the truing tool units 350, 350a, 35017, and 3500 simultaneously to pass coolant to all of the diamonds or truing tools 353 during a truingoperation.

A control valve 525 is provided for controlling the admission to and exhaust of fluid from the coolant control valve 5I6. The control valve 525 comprises a slidably mounted valve member 526 havinga valve chamber 521 formed in the periphery thereof. The valve member 526 is provided with a central passage 528. A compression spring 529 serves normally to hold the valve member 526 in a right-hand end position. A solenoid S4 is provided which when energized serves to shift the valve member 526 toward the left to reverse the direction of flow of fluid to the coolant control valve 5I6. As illustrated in Fig. 4 when fluid under pressure is passed through the main pressure line I38, it passes through a pipe 530 into the valve chamber 521 and through the pipe 519 to shift the valve member 5l1 toward the right to convey coolant to the grindingwheels. Similarly when the soleonid S4 is energized, the valve member 526 is shifted toward the left so that fluid under pressure from the pipe 530 entering the valve chamber 521'passes through the pipe 52I .to cause the valve member 511 .to move toward the left thereby passing coolant fluid from the supply pipe 515 to the pipe 522. to supply coolant fluid to all of the diamonds or truing tools 353 during a truing operation.

The operation of the improved grinding machine will be readily apparent from the foregoing disclosure. A main power switch (not shown) is closed so that power lines LI and L2 are connected with a source of power. A switch 535 is actuated to close a circuit to start the grinding wheel driving motor 102. Closing of the switch v535 also energizes a relay MW to set up a holding circuit. Astop switch 536 is provided to facilitate stopping the wheel motor 102 when desired. A pushbutton switch 531 is provided to facilitate closing a circuit to energize a relay switch CR1 5. The normally open contacts of relay CRI5 are connected in series with the normally closed contacts of limit switch LS1 so that when relay CR1 5 is energized, if the normally closed contacts'of LS1 are closed, the work driving motor-50 is started. As previously described, the normally closed contacts of the limit switch LSlare opened when the wheel slide moves rearwardly to an inoperative position. It will be readily apparent that after the pushbutton switch 531 has been initially actuated, the opening and closing of the normallyclosed contests of the limit switch LS1 will control the starting and stoppin of the work drive motor as the wheel slide is moved to and from anoperative position. When relay CR1 3 is energized, the nor- .mally open contacts thereof arejclosed and serve to energize-a relayMC to close the normally open 

